Study On Thermal Fatigue Resistance Of Biomimetic Coupling Brake Disc Materials Treated By Cast-in Process

Brake disc is an important part of vehicle which can braking performance and transportation security. With the rapid development of the construction of railways, the train speed is enhanced gradually.. During the eighth five-year plan, A quasi high speed train with mph of 160 km/h was produced,. Moreover, a faster train which has mph of 200 km/h was also made in another five-years plan.. Since Since 1970s,our country has raise the train speed for six times, the length of train line over 160km/mph has been to 7700 km. Under the above situations,, the brake disc of passenger train and freight train in China is facing with reduction of the life, high frequency servicing and decline of braking effect, mainly because the train braking power is the third power of speed. During the The braking progress of high-speed train, the brake disc resist tremendous breakdown friction force or dynamic friction force from the brake pads, the enormous power was transfered into heat energy, and was absorbed by the brake disc. The surface temperature rises rapidly because of cooling, so that the brake disc temperature falls. Brake disc endures vary temperature in the process of the braking, many thermal fatigue cracks grow in the brake area, so that brake disc is broken. Therefore, under the premise that conveyance tool overall to high speed development, now brake function and service life of brake disc far can't satisfy high speed vehicle circulate the thermal fatigue research of brake disc is a representative orientation in the field of the thermal fatigue research.Biomimetic is one of the most effective methods for designing and producing new materials in the future. In fact, biology not only can adapt to the environment, but also can satisfy its survival with the lowest energy and matter cost. Researches indicated that the surface shape, the structure and the materials could be coupled by different biology to make the max adaptability to their survival environment. The work which had been done by our research group shows that the thermal fatigue resistance of brake disk material can be enhanced by laser surface treating technology. However, due to the failure standard of brake disk, the depth of biomimetic coupling unit can not ensure its long-standing. Therefore, in this paper, the cast-in technology was used for biomimetic coupling treating to improve thermal fatigue resistance of brake disk materials, and vermicular cast iron was made as the base materials, H13 steel was made as cast-in biomimetic unit materials. The main contents of this research contain feasibility analysis, microstructure and micro-hardness of biomimetic unit, effects of shape, size and distance of unit on thermal fatigue resistance, and effects of coating alloying power on thermal fatigue resistance of cast-in biomimetic coupling materials. The conclusions are as following:1. The biomimetic coupling unit consists of four areas, including within unit, interface, phase transformation region,celerity cooling region and substrate region. Microstructures of the within unit is the same as interface, but with different size. The structure of the celerity cooling erea is ledeburite, and there is a metallurgy combining in the interface region.2. When shapes of the biomimetic coupling units are similar, the bigger the biomimetic coupling unit, the bigger celerity cooling region is. Contrarily, when shapes of the biomimetic coupling units are different, the better microstructures uniformity in the interface region of column biomimetic coupling unit, the less stress convergence is.3. Different shape unit makes different thermal fatigue resistance of biomimetic samples, and they are sorted as rotundity > squareness > striation. In the experiment bound, the bigger the biomimetic coupling units ,the worse the thermal fatigue behavior is; the bigger space between the biomimetic coupling units, the less the main crack length and the more crack quantity are.4. Column unit likes the column in the matrix, and thermal cracks has no choice but to round the unit or change the propagation direction; the dyke units act as dykes to bridge meet the crack or terminate the crack by reducing the volume of units and increasing the number of units, so it will improve the thermal fatigue property.5. Bepowdering alloy powder (Si,Ni,Cr) with different content has an improvement on the thermal fatigue property. The more bepowdering Si on the flank of the biomimetic coupling units, the less the main crack length and crack quantity are. With the more bepowdering Ni on the flank of the biomimetic coupling units, the less the main crack length and the more crack quantity are. The more bepowdering Cr on the flank of the biomimetic coupling units, the more main crack length and crack quantity are. Bepowdering Si on the flank of the biomimetic coupling units have the best thermal fatigue behavior, while bepowdering Ni on the flank of the biomimetic coupling units better than the bepowdering Cr. Bepowdering different alloy on the flank of the biomimetic coupling units are better than nothing on the flank of the biomimetic coupling units...